1. Field of the Invention
The present invention relates to a vehicle motion control apparatus.
2. Description of the Related Art
JP2003-170822A (see FIG. 6) discloses, for a driving force distribution device that distributes the driving force to the right and left wheels in order to control a vehicle yaw moment, a technology of performing yaw rate feedback control and slip angle feedback control on the driving force distribution amount based on an accelerator open level, an engine rev speed, a vehicle speed, a front-wheel turning angle, a lateral direction acceleration, a yaw rate, and vehicle-body sideslip angle (may also be called a vehicle slip angle), etc.
Also, there are known a control device of controlling respective driving forces of the right and left wheels based on a vehicle slip angle in order to control a yaw moment, and a technology of correcting/controlling the front-wheel turning angle based on a vehicle slip angle.
JPH09-99826A (see FIGS. 2 to 7 and paragraphs from 0077 to 0081) discloses a control device which calculates a target yaw moment from the slip angle of a rear wheel axis and the slip-angle velocity thereof in order to control respective driving forces of the right and left wheels, thereby controlling the yaw moment of a vehicle.
Japan Patent No. 4143111 (see FIGS. 1 and 2) discloses a recent vehicle motion control apparatus which improves the turning characteristic of allowing a vehicle to turn as a driver intends, prevents the vehicle from spinning, and suppresses a false operation and an excessive control. Such a vehicle motion control apparatus includes a feedback distributing/calculating means which compensatingly calculates a virtual external force to be fed back to a motional model of the vehicle based on a deviation between a vehicle first model state quantity (corresponding to a “reference attitude-state quantity” of the present invention) based on the motional model of the vehicle and a vehicle first actual state quantity (corresponding to an “actual attitude-state quantity” of the present invention), and which calculates a yaw moment, etc., to be fed back to the driving amount of an actuator that generates a vehicle motion.
In a vehicle motion control apparatus such as those disclosed in Japanese Patent No. 4143111, however, a vehicle body actual slip angle is used as a first actual state quantity of the vehicle and a reference vehicle body slip angle is used as a first model state quantity of the vehicle, and a feedback control is performed such that the difference between them becomes 0. Therefore, the accuracy of the estimation calculation of the vehicle body actual slip angle directly affects the motion control performance of the vehicle. It is difficult to improve the estimation accuracy of the vehicle body actual slip angle. When the accuracy of the estimation of the vehicle body actual slip angle is seriously decreased, the motion control performance of the vehicle is also decreased, which may give unnatural feeling to a driver.